On the impact of the turbulent/non-turbulent interface on differential diffusion in a turbulent jet flow
On the impact of the turbulent/non-turbulent interface on differential diffusion in a turbulent jet flow
复制标题
湍流/非湍流界面对湍流射流中差异扩散的影响
DOI：
10.1017/jfm.2016.471
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发表时间：
2016
影响因子：
3.7
通讯作者：
Christian Hasse
中科院分区：
文献类型：
--
作者：
F. Hunger;M. Gauding;Christian Hasse
分别具有施密特数为1和0.25的两个被动标量的微分扩散的效果，使用直接数值模拟的时间演变射流。研究的目的是双重的：（i）比较湍流/非湍流（T/NT）界面的位置，使用单位和低施密特数标量之间的标量标准;和（ii）确定的T/NT界面上的微分扩散的影响。对于后者，使用涡度准则检测T/NT界面。为了量化差分扩散的影响，归一化差分扩散参数进行了分析，清楚地显示了在T/NT接口的差分扩散的主导地位。的标量差异的输运方程，然后评估，这表明，差分扩散起源于接口。此外，被动标量之间的分离，由于差分扩散，使用传统的和有条件的统计接口距离进行了研究。由于微分扩散已知存在于大尺度和小尺度，它们之间的连接使用标量耗散率进行分析。此外，负责的两个标量的离开的物理机制进行了分析，使用标量梯度对齐，扩散通量的比率和标量梯度的输运方程。
The effect of differential diffusion of two passive scalars having Schmidt numbers of unity and 0.25, respectively, is investigated using direct numerical simulation of a temporally evolving jet. The objective of the research is twofold: (i) to compare the turbulent/non-turbulent (T/NT) interface position using the scalar criterion between the unity- and low-Schmidt-number scalar; and (ii) to determine the impact of the T/NT interface on differential diffusion. For the latter, the T/NT interface is detected using the vorticity criterion. To quantify the effect of differential diffusion, a normalised differential diffusion parameter is analysed, clearly showing the dominance of differential diffusion at the T/NT interface. A transport equation for the scalar differences is then evaluated, which shows that differential diffusion originates at the interface. Further, the separation between the passive scalars, arising due to differential diffusion, is studied using conventional and conditional statistics with respect to the interface distance. Since differential diffusion is known to be present at large and small scales, the connection between them is analysed using the scalar dissipation rate. Moreover, the physical mechanism responsible for the departure of the two scalars is analysed using the scalar gradient alignment, the ratio of the diffusive fluxes and by a transport equation for the scalar gradients.